1. Field of the Invention
The present invention relates in general to an internal combustion engine equipped with rotary valves and more particular to a valve operating mechanism for such an internal combustion engine.
2. Description of the Prior Art
A popet type intake or exhaust valve in an internal combustion engine involves a responsive delay due to its jumping at high-speed and is causative of surging, noise, etc. Such disadvantages can be overcome by the use of a rotary valve as is well known in the art. The rotary valve can be suitably made of ceramics since it is less liable to be subjected to an impact load as compared with the popet valve.
A prior art rotary valve operating mechanism disclosed in Japanese Patent Provisional Publication No. 59-32608 is adapted so that the valves rotate continuously in one direction. Another prior art mechanism disclosed in Japanese Patent Provisional Publication No. 62-203907 is adapted so that the valves oscilate 90.degree. between a valve opening position and a valve closing position.
A disadvantage of the first mentioned prior art mechanism is that a difficult work is required for adjusting the rotational speed of the rotary valve in relation to the angle of rotation of the crankshaft and thereby adjusting the valve opening and closing timings in order to, for example, make the valve open for a longer period.
A disadvantage of the second mentioned prior ar mechanism is that its durability is poor. This is because the valve in a position of closing the intake or exhaust port is exposed to the gases of a high temperature and high pressure at a portion facing the combustion chamber and to the gases of a low temperature and low pressure at a portion facing an intake pipe or an exhaust pipe. Due to this, the valve is subjected to great force and heat at the particular portion repeatedly so that local fatigue and wear of the valve, excessive wear of a vavle seat and large thermal stress due to the partial heating of the valve are liable to be caused.